Projected capacitive touch panels are used very widely today in mobile devices like smartphones, tablets etc. While they enable a display area to be reused for touch, they do not offer the same user experience of a pressure sensitive keyboard with tactile feedback to the finger.
For dedicated keyboards, in U.S. Pat. No. 8,139,035 B2 titled “TOUCH SENSITIVE KEYPAD WITH TACTILE FEEDBACK,” a touch sensitive surface is placed on top of a mechanical keyboard switch arrangement that provides tactile feedback, while the switch arrangement itself has electrical connectivity for indicating touch.
Very low profile mechanical keyboards have a limited electrical contact life though the tactile life of each key can be significantly larger. It is expensive to replace these keyboards in notebook PCs.
United States patent application US 2010/00860593 A1, published Mar. 11, 2010, for PHASE COMPENSATION FOR MULTI-STIMULUS CONTROLLER, describe the operation of a projected capacitance touch panel. It is referenced for the description of prior art regarding the operation of the projected capacitance touch panel.